1. Field of the Invention
Embodiments relate generally to optical diffraction grating apparatus, such as but not limited to Fresnel zone lens apparatus. More particularly, embodiments relate to enhanced performance optical diffraction grating apparatus, such as but not limited to enhanced performance Fresnel zone lens apparatus.
2. Description of the Related Art
As technology has advanced, the use of electro-optic principles and electro-optic devices in place of mechano-optic principles and mechano-optic devices has become more prevalent in systems including but not limited to optical imaging systems. A particular example of such a transition from mechano-optic principles and mechano-optic devices to electro-optical principles and electro-optical devices is represented by the transition from conventional photography and imaging that uses photographic film and mechanically controlled cameras, to digital photography and imaging that uses electronic sensor based imaging arrays as an imaging means.
Often included within electro-optical imaging systems are lenses that are intended to focus an optical image at a focal plane. Such lenses often operate by refraction of light incident upon a particular lens, but alternative lens constructions that operate by a diffraction of light incident upon a particular lens are also known. Of such lenses that operate by diffraction of light incident upon a particular lens, a Fresnel zone lens is a common and representative example.
A two-dimensional Fresnel zone lens generally comprises concentric rings either located and formed over a substrate, or integral with a substrate, where each of the plurality of concentric rings has either: (1) the same zone radius (i.e., to provide a sinusoidal Fresnel zone lens); or (2) the same zone area (i.e., to provide a binary Fresnel zone lens). Sinusoidal Fresnel zone lenses are desirable insofar as sinusoidal Fresnel zone lenses provide a single image at a single focal plane whose distance from the sinusoidal Fresnel zone lens is determined by the zone radius for a particular incident radiation wavelength. Alternatively, binary Fresnel zone lenses are desirable insofar as they provide an image at a primary focal plane, in addition to several subsidiary images at several subsidiary focal planes.
While Fresnel zone lenses are popular and desirable within the optical device and optical imaging art, Fresnel zone lenses are nonetheless not entirely without problems. In that regard, desirable are Fresnel zone lenses that may operate with enhanced flexibility and efficiency within the context of systems including but not limited to optical imaging systems.